The catalytic properties, anomalous behavior, mechanism of action and important structural characteristics of homogeneous mammalian arylsulfatase enzymes will be studied. The chemical nature of turnover-modified aryl sulfatase A, a nearly inactive enzyme form which is produced during the catalytic process, will be examined in order to determine how the enzyme brings about is own inactivation. A novel, powerful and widely applicable method for the purification of most mammalian aryl sulfatase enzymes will be explored in detail. A sensitive assay for human urine aryl sulfatase will be developed.